Heap-use-after-free in WebCore::GraphicsContext::drawImage

Replaced getShapeImageAndRect() in ShapeOutsideInfo.cpp with
ShapeOutsideInfo::createShapeForImage(). The original function
failed to protect the PassRefPtr return value returned by StyleImage::image(). 

BUG=378469

Review URL: https://codereview.chromium.org/305173003

git-svn-id: svn://svn.chromium.org/blink/trunk@175176 bbb929c8-8fbe-4397-9dbb-9b2b20218538